Method of preparation of crosslinked blends of amorphous and crystalline polymers

ABSTRACT

The present invention is broadly directed to a process for copolymerizing one or more alpha-olefins and one or more di-olefin monomers in the presence of at least one stereospecific metallocene catalyst system and at least one non-stereospecific metallocene catalyst system. Crosslinking of at least a portion of the mixture of polymer segments is accomplished during the polymerization of the composition by incorporation of single di-olefin comonomers into two polymer segments.

FIELD OF THE INVENTION

This invention relates to a thermoplastic composition which is a mixtureof crystalline and amorphous polyolefin copolymers. This inventionfurther relates to a process to produce such thermoplastic compositionsby copolymerizing alpha-olefins and α,ω-dienes using two separatecatalyst systems.

BACKGROUND INFORMATION

It is well recognized that amorphous polypropylene (aPP), even at a veryhigh molecular weight (e.g. M_(w)>1000,000 g/cc) is a soft, rubbery,gel-like material which possesses very low crystallinity and thereforepoor physical properties. Because of its poor mechanical strength, thismaterial has found few practical uses compared to isotacticpolypropylene (iPP), which has crystallinity and therefore bettermechanical properties.

Individual polyolefins having certain characteristics are often blendedtogether in the hopes of combining the positive attributes of thecomponents. Typically, however, the result is a blend which displays aweighted average of the individual properties of the individual resins.

For example EP 0 527 589 discloses blends of flexible low molecularweight amorphous polypropylene with higher molecular weight isotacticpolypropylene to obtain compositions with balanced mechanical strengthand flexibility. These compositions show better flexibility compared tothe isotactic polypropylene alone, but the elastic recovery propertiesare still poor.

U.S. Pat. No. 5,539,056 discloses polyolefin compositions comprising ablend of amorphous poly-alpha-olefin having a weight average molecularweight (M_(w)) of at least about 150,000 and a crystallinepoly-alpha-olefin having an M_(w) of less than about 300,000 and lessthan that of the amorphous poly-alpha-olefin. These compositions wereproduced by polymerizing alpha-olefin in the presence of two differentcyclopentadienyl transition metal compounds or by producing the polymersindependently and subsequently blending them together.

EP 0 366 411 discloses a graft polymer having an EPDM backbone withpolypropylene grafted thereto at one or more of the diene monomer sitesthrough the use of a two-step process using a different Ziegler-Nattacatalyst system in each step. This graft polymer is stated to be usefulfor improving the impact properties in blended polypropylenecompositions.

Although each of the polymers described in the above references has newand interesting properties, there remains a need for new compositionsoffering other new and different balances of mechanical propertiescontrollably tailored for a variety of end uses. It would be desirableto find a composition that is very strong yet having both goodflexibility and elasticity characteristics. It would further bedesirable to produce such a composition with a minimum of processingsteps.

SUMMARY OF THE INVENTION

The present invention is broadly directed to a polyolefin polymercomposition produced by copolymerizing one or more C₃ or higheralpha-olefins and one or more di-vinyl monomers in the presence of atleast one stereospecific metallocene catalyst system and at least onenon-stereospecific metallocene catalyst system in the samepolymerization medium. The polymer composition so produced containsamorphous polymer segments and crystalline polymer segments in which atleast some of the segments are crosslinked. Both the amorphous and thecrystalline polymer segments are copolymers of one or more alpha-olefinsand one or more monomers having at least two olefinically unsaturatedbonds. Both of these unsaturated bonds are suitable for and readilyincorporated into a growing polymer chain by coordination polymerizationusing either the stereospecific or the non-stereospecific catalystsindependently such that the di-olefin is incorporated into polymersegments produced by both catalysts in the mixed catalyst systemaccording to this invention. In a preferred embodiment these monomershaving at least two olefinically unsaturated bonds are di-olefins,preferably di-vinyl monomers. Crosslinking of at least a portion of themixture of polymer segments is accomplished during the polymerization ofthe composition by incorporation of a portion of the di-vinyl comonomersinto two polymer segments. At least a portion of the di-vinyl monomersare polymerized into two polymer segments, thus producing a crosslinkbetween those segments.

DETAILED DESCRIPTION OF THE INVENTION

In a preferred embodiment, the polyolefin polymer composition of thisinvention is a blend of polymeric segments which are crosslinked or inwhich at least a portion of the segments are joined chemically throughcarbon-to-carbon bonds. This blend includes amorphous polymer segmentsand crystalline polymer segments. In a preferred embodiment, theamorphous polymer segments and the crystalline polymer segments are eachcopolymers of one or more alpha-olefins and one or more di-olefinmonomers in which both of the double bonds can be copolymerized with theone or more alpha-olefins using both the stereospecific or thenon-stereospecific catalyst simultaneously.

The polymerization of both the amorphous and the crystalline polymersegments is performed in a single step. In other words, bothpolymerizations are carried out simultaneously with both catalystspresent in the same reaction medium. Both the type and amount of thediolefin monomer are selected to produce a sufficient amount ofcrosslinking of polymer segments to produce the desired physicalproperties in the final composition. Crosslinking, for purposes of thisinvention, refers to the connection of two polymer segments byincorporation of each double bond of a diolefin monomer into twodifferent polymer segments. The polymer segments so connected can be thesame or different, with respect to their crystallinity. Three or morepolymer segments may also be connected via incorporation of two or morediolefins in on polymer segment into two other polymer segments.

In a particularly preferred embodiment, the product produced is a blendof isotactic polypropylene segments and atactic polypropylene segmentswith sufficient crosslinking via diene incorporation into both types ofsegments to produce an improved balance of properties in the bulkcomposition. Polymer or polypropylene segments, as used herein, areintended to refer to copolymers containing the selected diolefinmonomers as a minor constituent. The crosslinked final compositioncontains a mixture of linkage types via incorporation of single diolefinmonomers into two separate polymer segment. These linkage types includeconnections between two amorphous copolymer segments, connectionsbetween two said crystalline copolymer segments, and connections betweenamorphous copolymer segments and crystalline copolymer segments. Thepresence of these crosslinked structures, produced by dieneincorporation into the growing segments of the crystalline/amorphouspolymer blend result in new and different physical properties versusthose found in the prior art.

Monomers

A primary consideration for selection of the monomer, or combinations ofmonomers, is that, both crystalline and amorphous polymer segments canbe formed with the proper selection of two or more different metallocenecatalyst systems. It is further necessary that the level ofincorporation of the diolefin monomer into the crystalline segments belimited to an amount that will not substantially alter itscrystallinity. Yet another reason to limit the addition of diolefinmonomer is to limit the level of crosslinking to a level such that theoverall composition remains a thermoplastic.

The α-olefins include linear, branched, or ring-containing C₃ to C₃₀prochiral α-olefins or combinations thereof capable of being polymerizedby both the stereospecific and the non-stereospecific catalystsselected. Prochiral, as used herein, refers to monomers that favor theformation of isotactic or syndiotactic polymer when polymerized usingthe selected stereospecific catalyst(s). Some embodiments select theα-olefins from C₃ to C₂₀ alpha olefins.

Preferred linear α-olefins include C₃ to C₈ α-olefins, more preferablypropylene, 1-butene, 1-hexene, and 1-octene, even more preferablypropylene or 1-butene. Preferred branched α-olefins include4-methyl-1-pentene, 3-methyl-1-pentene, and 3,5,5-trimethyl-1-hexene.

Preferred ring-containing α-olefins include as a ring structure at leastone aromatic-group. Some embodiments select a combination of propyleneand 1-butene as the alpha olefin.

Preferred aromatic-group-containing monomers contain up to 30 carbonatoms. Suitable aromatic-group-containing monomers comprise at least onearomatic structure, preferably from one to three, more preferably aphenyl, indenyl, fluorenyl, or naphthyl moiety. Thearomatic-group-containing monomer further comprises at least onepolymerizable double bond such that after polymerization, the aromaticstructure will be pendant from the polymer backbone. Preferredaromatic-group-containing monomers contain at least one aromaticstructure appended to a polymerizable olefinic moiety. The polymerizableolefinic moiety can be linear, branched, cyclic-containing, or a mixtureof these structures. When the polymerizable olefinic moiety contains acyclic structure, the cyclic structure and the aromatic structure canshare 0, 1, or 2 carbons. The polymerizable olefinic moiety and/or thearomatic group can also have from one to all of the hydrogen atomssubstituted with linear or branched alkyl groups containing from 1 to 4carbon atoms. Particularly preferred aromatic monomers include styrene,alpha-methylstyrene, vinyltoluenes, vinylnaphthalene, allyl benzene, andindene, especially styrene and allyl benzene.

Preferred diolefin monomers useful in this invention include anyhydrocarbon structure, preferably C₄ to C₃₀, having at least twounsaturated bonds, wherein at least two of the unsaturated bonds arereadily incorporated into a polymer by either the stereospecific or thenon-stereospecific catalyst(s). It is further preferred that thediolefin monomers be selected from α,ω-diene monomers (i.e. di-vinylmonomers) suitable for copolymerization with the selectedalpha-olefin(s) using each of the selected metallocene catalyst systems.More preferably, the diolefin monomers are linear di-vinyl monomers,most preferably those containing from 4 to 30 carbon atoms. Preferreddiolefin monomers according to this invention should contain no polargroups and should not act as a poison to any of the selected catalysts.Some embodiments select the diolefin molecules such that each olefinicgroup of the diolefin has substantially equal reactivity undermetallocene polymerization conditions as the other.

Catalysts

Non-stereospecific catalysts for the production of the amorphous polymersegments (atactic alpha-olefin-diene copolymers) of this inventioninclude any catalyst system capable of copolymerizing the selectedalpha-olefin monomer(s) and diolefin monomer(s). Such catalysts are wellknown to those skilled in the art. For additional detail on suchcatalysts, reference can be made to U.S. Pat. No. 5,723,560, which isfully incorporated by reference herein for purposes of U.S. patentpractice.

Illustrative, but not limiting examples of preferred non-stereospecificmetallocene catalysts are:

[dimethylsilanediyl(tetramethylcyclopentadienyl)(cyclododecylamindo)]metaldichloride;

[dimethylsilanediyl(tetramethylcyclopentadienyl)(t-butylamido)]metaldichloride; and

[dimethylsilanediyl(tetramethylcyclopentadienyl)(exo-2-norbornyl)]metaldichloride;

wherein the metal can chosen from Zr, Hf, or Ti, preferably Ti.

Stereospecific catalysts for the production of the crystalline polymersegments (isotactic or syndiotactic alpha-olefin-diene copolymers) ofthis invention include any catalyst system capable of copolymerizing theselect alpha-olefin monomer(s) and diolefin monomer(s). Suchstereospecific catalysts should at the same time polymerize thealpha-olefin monomer(s) in a stereospecific structure such that thecrystalline polymer segments contain isotactic or syndiotactic monomersequences sufficient to produce a heat of fusion, as measured by DSC, of10 J/g or more. For additional detail on such catalysts, reference canbe made to U.S. Pat. No. 5,770,753 and to W. Spaleck, et al., “TheInfluence of Aromatic Substituents on the Polymerization Behavior ofBridged Zirconocene Catalysts,” Organometallics, 13, 954-963 (1994),both of which are fully incorporated by reference herein for purposes ofU.S. patent practice.

Illustrative, but not limiting examples of preferred stereospecificmetallocene catalysts are the racemic isomers of:

[dimethylsilanediylbis(2-methyl-4-phenylindenyl)]metal dichloride;

[dimethylsilanediylbis(2-methyl)]metal dichloride;

[dimethylsilanediylbis(indenyl)metal dichloride;

[dimethylsilanediylbis(indenyl)metal dimethyl;

[dimethylsilanediylbis(tetrahydroindenyl)metal dichloride;

[dimethylsilanediylbis(tetrahydroindenyl)metal dimethyl;

[dimethylsilanediylbis(indenyl)metal diethyl; and

[dibenzylsilanediylbis(indenyl)metal dimethyl;

wherein the metal can be chosen from Zr, Hf, or Ti, preferably Zr.

The activator for the mixed catalyst system of this invention (i.e. atleast one non-stereo-specific and at least on stereo-specific catalyst)can be used in conjunction with any activation system which promotescoordination catalysis, typically either an alumoxane or anon-coordinating anion activator.

Alumoxanes are well known in the art and methods for their productionare illustrated by U.S. Pat. Nos. 4,542,199; 4,544,762; 5,015,749; and5,041,585. A technique for preparing modified alumoxanes has beendisclosed in U.S. Pat. No. 5,041,584, and in EPA 0 516 476 and in EP 0561 476, all of which are fully incorporated herein by reference forpurposes of U.S. patent practice.

Descriptions of ionic catalysts for coordination polymerizationcomprised of metallocene cations activated by non-coordinating anionsappear in the early work in EP-A-0 277 003, EP-A-0 277 004 and U.S. Pat.No. 5,198,401 and WO-A-92/00333, all of which are fully incorporatedherein by reference for purposes of U.S. patent practice. These teach apreferred method of preparation wherein metallocenes (bis-Cp andmono-Cp) are protonated by an anionic precursors such that analkyl/hydride group is abstracted from a transition metal to make itboth cationic and charge-balanced by the non-coordinating anion.

The use of ionizing ionic compounds not containing an active proton butcapable of producing both the active metallocene cation and anoncoordinating anion is also known. For additional detail see, EP-A-0426 637 and EP-A-0 573 403, both of which are fully incorporated hereinby reference for purposes of U.S. patent practice. An additional methodof making the ionic catalysts uses ionizing anionic pre-cursors whichare initially neutral Lewis acids but form the cation and anion uponionizing reaction with the metallocene compounds, for example the use oftris(pentafluorophenyl) boron, as described in EP-A-0 520 732, which isfully incorporated herein by reference for purposes of U.S. patentpractice. Ionic catalysts for addition polymerization can also beprepared by oxidation of the metal centers of transition metal compoundsby anionic pre-cursors containing metallic oxidizing groups along withthe anion groups, as described in EP-A-0 495 375, which is fullyincorporated herein by reference for purposes of U.S. patent practice.

The catalyst system of this invention may be supported on an inertcarrier. Methods of supporting alumoxane activated metallocene catalystsystems are well known in the art. Methods of supporting ionic catalystscomprising metallocene cations and noncoordinating anions are describedin U.S. Pat. Nos. 5,057,475, 5,643,847, WO91/09882, WO 94/03506 andWO96/04320 888in co-pending U.S. Ser. No. 08/248,284, filed May 24,1994, now abandoned, all of which are fully incorporated herein byreference for purposes of U.S. patent practice.

Process

The polymerization processes forming the crosslinked blends of thisinvention are performed in a common reaction medium containing themonomers, both alpha-olefin(s) and di-olefin(s), at least onenon-stereo-specific metallocene catalyst system, and at least onestereo-specific metallocene catalyst system. “Alpha-olefin” and“di-olefin” are distinguished herein in that an alpha-olefin has onlyone double-bond that is readily polymerizable by both of the selectedcatalyst systems.

The catalyst systems employed in the method of the invention comprise acomplex formed upon admixture of the two or more catalyst componentswith one or more activator components. The catalyst system may beprepared by addition of the requisite catalysts as described above,preferably Group IV B transition metal catalysts, and activatorcomponents to an inert solvent in which olefin polymerization can becarried out by a solution, slurry, gas phase or bulk phasepolymerization procedure, most preferably a solution or slurrypolymerization process.

The catalyst system may be conveniently prepared by placing the selectedcatalyst components and the selected activator component, in any orderof addition, in an alkane or aromatic hydrocarbon solvent-preferably onewhich is also suitable for service as a polymerization diluent. When thehydrocarbon solvent utilized is also suitable for use as apolymerization diluent, the catalyst system may be prepared in situ inthe polymerization reactor. Alternatively, the catalyst system may beseparately prepared, in concentrated form, and added to thepolymerization diluent in a reactor. If desired, the components of thecatalyst system may be prepared as separate solutions and added to thepolymerization diluent in a reactor, in appropriate ratios, as issuitable for a continuous liquid phase polymerization reactionprocedure.

Alkane and aromatic hydrocarbons suitable as solvents for formation ofthe catalyst system and also as a polymerization diluent are exemplifiedby, but are not necessarily limited to, straight and branched chainhydrocarbons such as isobutane, butane, pentane, hexane, heptane, octaneand the like, cyclic and alicyclic hydrocarbons such as cyclohexane,cycloheptane, methylcyclohexane, methylcycloheptane and the like, andaromatic and alkyl-substituted aromatic compounds such as benzene,toluene, xylene and the like. Suitable solvents also include liquidolefins which may act as monomers or comonomers including propylene,1-butene, 1-hexene and the like.

At all times, the individual catalyst system components, as well as thecatalyst system once formed, are protected from oxygen and moisture.Therefore, the reactions to prepare the catalyst system are performed inan oxygen and moisture free atmosphere and, where the catalyst system isrecovered separately it is recovered in an oxygen and moisture freeatmosphere. Preferably, therefore, the reactions are performed in thepresence of an inert dry gas such as, for example, helium or nitrogen.

In a preferred embodiment of the process of this invention the catalystsystem is utilized in a slurry liquid phase or a high pressure fluidphase or gas phase polymerization of the alpha-olefin and diolefinmonomers. These processes may be employed singularly or in series. Theliquid phase process comprises the steps of contacting alpha-olefin anddiene monomers with the mixed catalyst system in a suitablepolymerization diluent and reacting said monomer in the presence of saidcatalyst system for a time and at a temperature sufficient to producethe crosslinked copolymer blends of this invention.

The catalyst system ingredients-that is, the catalysts, the activatorcomponent, and polymerization diluent-can be added to the reactionvessel rapidly or slowly. Conditions most preferred for thepolymerization process are those wherein the alpha-olefins and diolefinsare submitted to the reaction zone at pressures of from about 0.019 psia(0.131 kPa) to about 50,000 psia (345 MPa), preferably 50 (345 kPa) to1500 psia (10.34 MPa), more preferably 120 psia (827 kPa) to 1000 psia(6895 kPa), and the reaction temperature is maintained at from about−100° C. to about 300° C., preferably 0° C. to 180° C., more preferably30° C. to 120° C., even more preferably less than 90° C., mostpreferably less than 80° C.

In a preferred embodiment of the invention optimum results are obtainedwhen the total of the catalyst compounds are present in thepolymerization diluent in a concentration of from about 0.00001 to about1.0 millimoles/liter of diluent and the alumoxane component is presentin an amount to provide a molar aluminum to transition metal ratio offrom about 1:1 to about 20,000:1 or the ionic activator component ispresent in an amount to provide a molar activator to transition metalmolar ratio of from about 50:1 to about 1:20. Sufficient solvent shouldbe employed so as to provide adequate heat transfer away from thecatalyst components during reaction and to permit good mixing. A morepreferable range for the aluminum to transition metal molar ratio wouldbe 1:1 to 2000:1 and for an ionic activator to transition metal molarratio would be about 20:1 to about 1:5. The reaction time is preferablyfrom about 10 seconds to about 10 hours. These ratios are based on thetotal of both the stereospecific and the non-stereospecific catalysts.

In one preferred embodiment, wherein catalysts having similar activity(in terms of kg of polymer produced, per mole of transition metalcontained in the catalyst, per hour) to those used the examples beloware employed, the ratio of non-stereospecific catalyst to stereospecificcatalyst is preferably in the range of from 20:1 to 120:1, morepreferably from 30:1 to 110:1, even more preferably from 40:1 to 100:1.The activity level of the non-stereospecific to stereospecific catalystsemployed in the practice of this invention as it relates to the chosenmonomers and process conditions can be readily determined by methodswell known to those skilled in the art. For catalysts having differentactivity levels than those of the examples below, preferred compositionsare produced by selecting a ratio of non-stereospecific catalyst tostereospecific catalyst that would be expected to produce amorphouspolymer segments and crystalline polymer segments in a ratio in therange of from 2:1 to 20:1, more preferably from 3:1 to 10:1, even morepreferably from 4:1 to 8:1 (all ratios of amorphous to crystalline).

Scavengers may be used as described in pending U.S. patent applicationSer. No. 08/455,960, filed nMay 31, 1995, and WO 94/07927 which is fullyincorporated herein by reference for purposes of U.S. patent practice.

The diolefin monomer(s), preferably di-vinyl monomer(s), are added tothe reaction medium in an amount sufficient to produce a detectableamount of crosslinking but are limited to an amount such that the finalcomposition remains thermoplastic. For the purposes of this invention,the amount of crosslinking is determined using the crosslinking index gof the crosslinked polypropylene. The crosslinking index g is defined asthe ratio of the radius of gyration of the crosslinked polymer to theradius of gyration of a linear polymer g=[R_(g)]² _(cr)/[R_(g)]² _(lin).It is well known in the art that as the g value decreases, crosslinkingincreases. “R_(g)” stands for Radius of Gyration, and is measured usingMulti-Angle Laser Light Scattering (MALLS) equipment. “[R_(g)]_(cr)” isthe Radius of Gyration for the crosslinked polymer sample and“[R_(g)]_(lin)” is the Radius of Gyration for a linear polymer sample.

Crosslinking is indicated when the polymer radius of gyration deviatesfrom that measured for a linear polymer. The average deviation level wascalculated from GPC/MALLS data using the procedure outlined in theexamples below. First, the GPC/MALLS data was used to measure molecularweight averages (M_(w), M_(z)) and to measure polymer radius of gyrationas a function of absolute molecular weight. For polypropylene polymers,the MALLS measurement of R_(g) is particularly sensitive in the rangefrom 100,000 Daltons to about 2,000,000 Daltons. For this reason, thedata was then truncated outside this range. Weight-average values of gwere calculated from the data points that fall in the range of from thecharacteristic M_(w) of the polymer examined to the upper limit of2,000,000 Daltons. For any case in which some values of M_(w) that arebelow 100,000 Daltons, the weight average is calculated using only thosepoints between 100,000 Daltons and 2,000,000 Daltons.

Product

Amorphous poly-alpha-olefins, generally regarded to be atactic,noncrystalline and lacking in a molecular lattice structure which ischaracteristic of the solid state, tend to lack well defined meltingpoints. For purposes of this invention, amorphous and atactic aresynonymous and are intended to include that which is substantiallyamorphous or substantially atactic. An amorphous polymer segment isherein defined to mean a polymer segment that lacks or has a poorlydefined melting point and that further has little or no crystallinity.The amorphous product of this invention is substantially, preferablycompletely, atactic.

The amorphous alpha-olefin-diene copolymer segments preferably have aheat of fusion of 6 J/g or less, more preferably 4 J/g or less, evenmore preferably 2 J/g or less, and most preferably no detectable heat offusion.

The amorphous alpha-olefin-diene copolymer segments additionally have aglass transition temperature (T_(g)) which is lower than the usetemperature of the final composition of this invention. Preferably, thefinal composition of this invention has a T_(g) of 25° C. or less.

The weight average molecular weight of the alpha-olefin-diene copolymercan be between 10,000 to 5,000,000, preferably 80,000 to 500,000 g/molewith a MWD (M_(w)/M_(n)) between 1.5 to 40.0, more preferably betweenabout 1.8 to 5 and most preferably between 1.8 to 3.

The crystalline polymer segments contain crystallinity derived fromstereoregular segments, preferably isotactic or syndiotactic sequences,more preferably isotactic sequences, obtained by polymerization ofcontinuous sequences of the α-olefin monomers within the crystallinepolymer segments. Particularly preferred crystalline segments containpolypropylene-diene copolymers containing the di-vinyl monomer as thediene. The diene is present in an amount sufficient to produce thedesired level of crosslinking yet low enough to preserve the crystallinecharacter of the segments. The balance of crosslink density andcrystallinity help produce the new and useful balance of properties ofthe composition of this invention.

Preferred crystalline segments have an average alpha-olefin content,preferably propylene content, on a molar basis of from about 95% toabout 99.9%, more preferably from about 97% to about 99.8%, even morepreferably from about 99% to about 99.7%. The balance of the copolymeris one or more minor α-olefins as specified above and optionally minoramounts of one or more diene monomers.

The crystalline alpha-olefin diene copolymer segments preferably have aheat of fusion greater than or equal to about 56 J/g, more preferably inthe range of from about 76 J/g to about 170 J/g, and most preferablyfrom about 95 J/g to about 151 J/g. The crystallinity of thealpha-olefin copolymer arises from crystallizable stereoregularalpha-olefin sequences.

In another embodiment, the crystallinity of the alpha-olefin-dienecopolymer is expressed in terms of crystallinity percent. The thermalenergy for the highest order of polypropylene is estimated at 189 J/g.That is, 100% crystallinity is equal to 189 J/g. Therefore, according tothe aforementioned energy levels, the present invention preferably has apolypropylene crystallinity of greater than 30%, more preferably fromabout 40% to about 90%, and most preferably from about 50% to about 80%by weight as measured by DSC.

The weight average molecular weight of the alpha-olefin-diene copolymersegments can range from 10,000 to 500,000 g/mole, preferably 20,000 to400,000, more preferably 30,000 to 300,000.

Preferably, the alpha-olefin-diene copolymer of the present inventioncomprises a random crystallizable copolymer having a narrowcompositional distribution. The intermolecular composition distributionof the polymer is determined by thermal fractionation in a solvent. Atypical solvent is a saturated hydrocarbon such as hexane or heptane.This thermal fractionation procedure is described below. Typically,approximately 75% by weight and more preferably 85% by weight of thepolymer is isolated as one or two adjacent, soluble fraction with thebalance of the polymer in immediately preceding or succeeding fractions.Each of these fractions has a composition (wt. % ethylene content) witha difference of no greater than 20% (relative) and more preferably 10%(relative) of the average weight % ethylene content of thealpha-olefin-diene copolymer. The alpha-olefin-diene copolymer has anarrow compositional distribution if it meets the fractionation testoutlined above.

In a preferred embodiment, the final composition has a crosslinkingindex (g) of less than or equal to 1, more preferably less than or equalto 0.95, even more preferably less than or equal to 0.90. The amount ofcrosslinking increases as g decreases. As stated earlier, however,crosslinking should be limited in order to permit the final compositionto remain a thermoplastic. Therefore, preferred final compositions ofthis invention have less than 75 percent insolubles, more preferablyless than 50 percent insolubles, even more preferably less than 25percent insolubles, by weight as measured by ASTM D3616-95 using anappropriate solvent for gel content analysis. An appropriate solvent canbe determined by reference to Brandrup and Immergut, Polymer Handbook,3rd ed., Wiley (1989). A particularly preferred solvent forpolypropylene is 2-butoxyethanol.

Preferred compositions according to the invention have a weight averagemolecular weight (M_(w)), as measured by GPC/MALLS, in the range of from100,000 to 1,000,000 g/mole, more preferably from 200,000 to 900,000,even more preferably from 300,000 to 800,000.

Preferred compositions according to the invention have an initialmodulus, in the range of from 350 to 8,000 p.s.i. (2.4 to 55 MPa), morepreferably from 500 to 6,000 p.s.i. (3.4 to 41 MPa), even morepreferably from 1,000 to 5,000 p.s.i. (6.9 to 34 MPa).

Preferred compositions according to the invention have a tensilestrength greater than or equal to 350 p.s.i. (2.4 MPa), more preferablygreater than or equal to 500 p.s.i. (3.4 MPa), even more preferablygreater than or equal to 1000 p.s.i. (6.9 MPa).

Preferred compositions according to the invention have a recovery from100% strain of greater than or equal to 80%, more preferably greaterthan or equal to 85%, even more preferably greater than or equal to 90%.

Preferred compositions according to the invention are ductile and can bedrawn to at least 300% strain of their original length, more preferably400%, even more preferably 500%.

By appropriate selection of (1) the type and relative amounts of each ofthe catalyst components for use in the mixed catalyst system; (2) thetypes and the total and relative amounts of each monomer; (3) the typeand amount of activator used relative to the amount of catalyst; (4) thepolymerization diluent type and volume; (5) reaction temperature; and(6) reaction pressure, one can tailor the weight average molecularweight and balance of properties of the final composition to meet therequirements of a broad range of applications.

The compositions that are prepared in accordance with this invention canbe used to make a variety of products including films, fibers, foams,adhesives, and molded articles. Such products include, but are notlimited to, automotive applications, roofing, electrical insulation,sports apparel, household items, and plumbing applications. Automotiveapplications include door, trunk, and window seals, weather stripping,windshield wipers, wheel arch and wheel well liners, bumpers and bumpercovers, and flexible boots for moveable mechanical joints. Electricalapplications include use of the compositions of the invention alone orin a blend with other polymers as insulation for large and small gaugewire and cable. Sports apparel uses of the composition of the inventioninclude use in various forms of padding and in soles of shoes. Householdapplications include door and window seals, weather stripping, seals forappliances such as refrigerators and dishwashers, and gaskets and sealsfor plumbing.

The composition of this invention can be used in any of theseapplications either independently or as a component of a blend withother polymers and/or additives. When used in a blend, it can be eithera major or a minor component in the blend, or can itself be consideredan additive (e.g. a toughening agent for polypropylene). For example,one skilled in the art would be familiar with the use of additivestypically used selected applications such as, but not limited to, dyes,pigments, fillers, waxes, plasticizers, anti-oxidants, heat stabilizers,light stabilizers, anti-block agents, processing aids, and combinationsthereof, and further including fillers.

An advantage of the invention over that which is currently available isthe ability to customize the balance of properties over broad ranges ofcombinations while still utilizing a one step polymerization process.

EXAMPLES

Tables 1 through 3 show a comparison of qualities of compoundscontaining a mixture of atactic polypropylene and isotacticpolypropylene. Examples 2-5, 7-10, 15-18, 20-24, and 26-29 demonstratethe improved balance of properties of compositions according to thisinvention relative to comparative Examples 1, 6, 10-14, 19, and 25.

In comparative Example 1, 1,000 ml of toluene were charged into areactor followed by 2 ml of tri-isobutylaluminum (TIBAL) and 150 ml ofpropylene. After raising the reactor temperature to 60° C. with rapidstirring, 4.5 mg of a non-stereospecific catalyst, [dimethylsilanediyl(tetramethylcyclopentadienyl) (cyclododecylamido)] titanium dichloride(hereinafter Catalyst D), and 0.10 mg of a stereospecific catalyst,[dimethylsilanediylbis(2-methyl) ] zirconium dichloride (hereinafterCatalyst L), with 4.6 ml of 5% methylalumoxane (MAO) in ˜10 ml oftoluene were injected. Product yield was 44.8g.

For Examples 2-29, similar conditions, starting materials, andquantities were used to make other products containing both atacticpolypropylene and isotactic polypropylene, except where specifiedotherwise in Tables 1-3. The polymerization temperature for each examplewere either 60° C. or 85° C. as shown in Tables 1-3. Catalyst ratioswere varied intending to give target products with iPP contents rangingfrom approximately 11% to 50%.

For comparative purposes, several series of reactions were performed inwhich a second stereospecific catalyst,[dimethylsilanediylbis(2-methyl-4-phenylindenyl)] zirconium dichloride,(hereinafter Catalyst Q), which produces a significant percentage(˜70-80%) of vinyl end groups, was substituted for Catalyst L.

The conditions used for the inventive examples, which included diolefinincorporation, were similar to those without the diolefin monomer withthe exception that a small quantity of 1,9-decadiene (0.1-4.0 ml) wascharged as the diolefin monomer along with polypropylene as thealpha-olefin monomer. Evidence for the existence of crosslinking (viadiene incorporation) was determined indirectly through testing physicalproperties of the final compositions and GPC/MALLS analysis.

a) Compression Molding: Plaques suitable for physical property testingwere compression molded on a Carver hydraulic press. 6.5 g of polymerwas molded between brass plates (0.05″ thick) lined with Teflon™ coatedaluminum foil. A 0.033″ thick chase with a square opening 4″×4″ was usedto control sample thickness. After one minute of preheat at 170 ° or 180° C., under minimal pressure, the hydraulic load was gradually increasedto ˜10,000-15,000 lbs., at which it was held for three minutes.Subsequently the sample and molding plates were cooled for three minutesunder ˜10,000 to 15,000 lbs. load between the water cooled platens ofthe press. Plaques were allowed to equilibrate at room temperature for aminimum of one week prior to physical property testing.

b) Unidirectional Tensile Testing: Dogbones for tensile testing were cutfrom compression molded plaques using a mallet handle die. Specimendimensions were those specified in ASTM D 1708. Tensile properties weremeasure on an Instron™ model 4502 equipped with a 22.48 lb. load celland pneumatic jaws fitted with serrated grip faces. Deformation wasperformed at a constant crosshead speed of 5.0 in/min with a datasampling rate of 25 points/second. Jaw separation prior to testing was0.876″, from which strains were calculated assuming affine deformation.Initial modulus, stress and strain at yield (where evident), stress at100%, 200%, 300%, 400%, 500% and 1,000% strain, and stress and strain atbreak were calculated. A minimum of five specimens from each plaque wastested, the results being reported as the average value. All stressesquoted are “engineering” values, i.e. they are calculated based upon theoriginal cross-sectional area of the specimen, taking no account ofreduced cross-section as a function of increasing strain. Strain valuesin excess of 500% are questionable; most samples pulled out of the gripsto some extent at higher strains. Thus, the strain calculated fromcrosshead separation is larger than the strain experienced in the gaugeregion of the sample. This phenomenon was particularly apparent insamples that exhibited high degrees of strain hardening.

c) Elastic Recovery Testing: Elastic recovery experiments were performedon an MTS model 810 equipped with a 200 lb. load cell and pneumatic jawsfitted with serrated grip faces. Specimen dimensions were the same asthose used in tensile experiments. In order to maximize the amount ofdata available from a given sample a cyclic testing protocol was used.Each specimen was sequentially elongated to nominal strains of 100%,200%, 300%, 400%, 500% and (optionally) 1,000% at an elongation rate of5.0 in/min. Upon reaching each pre-determined strain level the crossheaddirection was immediately reversed, returning to its starting positionat a rate of 5.0 in/min. Examination of the tabulated data provides anestimate of the strain level at which stress drops to zero on eachreturn cycle. Recovery from each strain level is calculated accordingto:${{Rapid}\quad {recovery}\quad (\%)} = \frac{100\left( {S_{x} - S_{r}} \right)}{S_{x}}$

where:

S_(x)=Nominal strain (100%, 200% etc.)

S_(r)=Strain (%) at which stress drops to zero during return cycle

The rapid recovery and long term recovery values reported are theaverage of three specimens.

d) Differential Scanning Calorimetry: Differential scanning calorimetry(DSC) was performed on a TA Instruments model 2920. Samples weighingapproximately 7-10 mg were cut from compression molded pads and sealedin aluminum sample pans. Each sample was scanned from −50° C. to 200° C.at 10° C./min. After completion of the first melt, samples were cooledto −50° C. at 10° C./min. and a second melt was recorded under the sameconditions as the first. Integrated areas under peaks were measured andused to determine degrees of crystallinity. A value of 189 J/g was usedas the heat of fusion for 100% crystalline polypropylene. Peak meltingtemperatures were also noted.

e) Density Determination: The densities of samples cut from compressionmolded plaques were measured by flotation in an isopropanol/diethyleneglycol density gradient column.

f) Gel Permeation Chromotography/Multi-Angle Laser Light Scattering(GPC/MALLS)

The two main components for this test are: (a) a Waters Corporation 150C. high temperature GPC, equipped with a differential refractometer(DRI) used to measure the solution concentration used in the MALLSanalysis, and (b) a Wyatt Technology Dawn DSP MALLS detector.

The major components of the Wyatt Technology Dawn DSP MALLS detectorare: (a) a 30 mW, 488 nm argon ion laser, (b) an optical flow cell, and(c) an array of 17 photodiodes placed at different collection anglesabout the flow cell. A heated transfer line directs the fractions elutedfrom the columns into the flow cell, and then from the flow cell to theDRI. The incident laser beam is directed along the length of the cellbore. The flow cell and heated transfer line are maintained at 135 ° C.through internal heaters.

The sequence of events in a GPC-MALLS experiment is as follows:

1) A dilute polymer solution is injected by the 150 C. onto theseparation columns.

2) The columns separate the polymer molecules by geometric size, withthe largest molecules eluting first.

3) The polymer fractions pass through the MALLS detector which measuresthe scattering intensity as a function of angle.

4) The fractions then pass through the differential refractometer whichmeasures the polymer concentration.

5) The MALLS and DRI signals are matched up. The molecular weight andradius of gyration are then calculated for the polymer fractions.

Solvent for the GPC experiment was prepared by adding 6 grams ofbutylated hydroxy toluene (BHT) as an antioxidant to a 4 liter bottle of1,2,4 Trichlorobenzene (TCB)(Aldrich Reagent grade) and waiting for theBHT to solubilize. The TCB mixture was then filtered through a 0.7 μmglass prefilter and subsequently through a 0.1 μm teflon filter. Therewas an additional online 0.7 μm glass prefilter/0.22 μm teflon filterassembly between the high pressure pump and GPC columns. The TCB wasthen degassed with an online degasser (Phenomenex, Model DG-4000).

The polymer solution was prepared by decanting a portion of the mobilephase TCB into a separate container for use in the sample preparation.Polymer samples to be tested were collected and weighed and placed in avial with the amount needed to attain the desired concentration(typically C=2.0 mg/ml for a polyethylene sample of M_(w)≈100,000g/mole). The polymer concentration in the solvent was then determined at135° C. Relevant constants for TCB are: ρ_(RT)=1.4634 g/ml at roomtemperature, and ρ_(T=135° C.)=0.905×ρ_(RT).

The polymer solution was then heated to 160 ° C. for a period of ≈2hours with continuous agitation (100-150 rpm). The prepared sample wasthen placed in the carousel in the GPC injector compartment. The runconditions for the GPC-MALLS were: 3 Polymer Laboratory Mixed B typecolumns; 0.5 ml/minute nominal flow rate; 300 ml nominal injectionvolume; temperature of 135 ° C.; and 100 minutes run time per sampleinjection.

The injection volume was determined by weighing the GPC vials withsolution before and after the injection sequence. The weight differencedivided by ρ_(T=135° C.) was assumed to be the injection volume. Theflow rate was determined by weighing the amount of solvent collected inthe waste line in a ≈24 hour period. The flow rate was calculated bydividing the mass of TCB collected by the collection time minutes, andthan dividing by ρ_(T=135°) C.

Prior to running each sample the DRI detector and injector were purged.Flow rate in the apparatus was then increase to 0.5 ml/minute, and theDRI was allowed to stabilize for 8-9 hours before injecting the firstsample. The argon ion laser was turned on 1 to 1.5 hours before runningsamples by running the laser in idle mode for 20-30 minutes and thenswitching to full power in light regulation mode.

Samples were recorded in the sample queue in the Astra software asdescribed by the Astra manual and the Astra data collection was set for15 points per minute. Sample vials in a heated sample carousel were thenplaced into the Waters GPC 150 C. injector compartment. The GPC run wasthen started with a 20-30 minute initial delay before the firstinjection. After the last sample was run, the MALLS calibrationprocedure was performed to determine the calibration constant for dataanalysis.

The DRI signal from the Waters 150 C. GPC was input into the WyattTechnology MALLS detector hardware. The conversion factor between theDRI response to a sample concentration in the MALLS software (calledAstra) is referred to as Aux. 1 (short for Auxillary Input #1). The DRIwas calibrated in each carousel run by standard procedures such that thedata was analyzed using the concentration as measured by the DRIresponse instead of assuming 100% mass recovery. The MALLS detector wasthen calibrated by measuring the 90° TCB solvent scattering, and thencalculating an effective instrument constant from the Rayleigh ratioaccording to standard procedures prior to shutting off the laser. The 17photodiodes positioned around the scattering volume of the MALLSdetector at different scattering angles were then normalized accordingto the manufacturer's recommended procedures. The interdetector volumebetween the MALLS detector and the DRI was performed according to theprocedure as recommended by the manufacturer.

The molecular weights of the compositions and the occurrence ofcrosslinking in a given polymer sample were determined by usingGPC-MALLS. Crosslinking was determined by establishing the polymerradius of gyration, Rg, as a function of molecular weight and comonomercontent for linear polymers, then using the measured coil dimensions ofthe polymer sample in question as a function of molecular weight tocalculate a branching indices <g>_(w) and <g>_(z) for the given polymersample.$g_{w} = \frac{{Rg}_{w_{—}{crosslinked}}^{2}}{{Rg}_{w_{—}{linear}}^{2}}$$g_{z} = \frac{{Rg}_{z_{—}{crosslinked}}^{2}}{{Rg}_{z_{—}{linear}}^{2}}$

where C_(i), M_(i), and Rg_(i) (i refers to the second moment, w, or thethird moment, z) are the measured (by GPC-MALLS) polymer concentration,molecular weight, and radius of gyration at each retention volume slice.

Tables 1-3 show the physical characteristics of the compositions of theinvention produced using a stereospecific/non-stereospecific mixedmetallocene catalyst system with propylene and di-olefin monomers. Alsoshown in these tables are comparative examples of similar compositionsproduced either with a single catalyst and propylene and di-vinylmonomers or a mixed catalyst system without the di-vinyl comonomer.

TABLE 1 Comparison of Mechanical Properties, Composition of theInvention vs. Blends Example 1 2 3 4 5 6 7 8 9 10 Comparative/InventionC I I I I C I I I I Non-stereospecific catalyst (NSS) D D D D D D D D DD Stereospecific catalyst (SS) L L L L L L L L L L Catalyst ratio(NSS/SS) 45/1 45/1 45/1 45/1 45/1 93/1 93/1 93/1 93/1 93/1 Targeta-PP/i-PP ratio 4/1 4/1 4/1 4/1 4/1 8/1 8/1 8/1 8/1 8/1 Diolefin used(ml) 0.0 0.2 0.4 1.0 2.0 0 0.5 11.0 2.0 4.0 Diolefin (ppm) 0 1,852 3,7049,259 18,519 0 4,630 9,259 18,519 37,037 Yield (g) 44.8 33.5 30.7 36.031.1 59.1 45.0 51.4 54.1 39.2 Polymerization Temp. (° C.) 60 60 60 60 6085 85 85 85 85 Density (g/cm³) 0.8690 0.8810 0.8800 0.8860 0.8800 0.87500.9000 0.8975 0.8950 0.8965 T_(m) (° C.), 2nd melt 141 145 140 140 138124 131 129 132 121 Heat of fusion (J/g) 13 28 20 26 26 8 24 31 33 —Degree of crystallinity (%) 7 15 11 14 14 4 13 16 17 7 M_(n) (× 1,000)166 138 159 150 166 38 37 39 — 43 M_(w) (× 1,000) 355 318 356 404 530 94118 122 135 182 M_(z) (× 1,000) 596 588 710 853 1,450 174 249 268 401561 M_(w)/M_(n) 2.14 2.30 2.24 2.69 3.19 2.43 3.16 3.10 — 4.19M_(z)/M_(n) 3.59 4.26 4.47 5.69 8.73 4.50 6.68 6.80 — 12.93 g_(w) 1.051.00 0.95 0.89 0.73 0.99 0.96 0.91 0.76 0.61 g_(z) 1.05 0.98 0.91 0.840.64 1.00 0.94 0.88 0.71 0.54 Initial modulus (PSI) 722 2,680 2,1854,533 4,686 756 5,821 8,097 7,321 1,845 Yield stress (PSI) — — — — — 98375 481 484 207 Yield strain (%) — — — — — 57 31 27 29 58 Stress at 100%strain 180 347 353 527 618 91 310 404 432 203 Stress at 500% strain 196481 566 896 1,300 23 — 393 509 225 Tensile strength (PSI) 351 764 1,1581,058 1,480 98 375 481 817 491 Strain at break (%) 1,919 911 1,116 626595 — 380 958 1,108 1,703 Recovery from 100% strain 84 85 85 85 83 66 6160 65 72 Recovery from 500% strain 76 77 79 76 73 — 38 42 50 64 Recoveryfrom 1,000% strain 71 — 72 — — — — — — 66

TABLE 2 Comparison of Mechanical Properties, Composition of theInvention vs. Blends Example 11 12 13 14 15 16 17 18Comparative/Invention C C C C I I I Non-stereospecific catalyst (NSS) DD D D D D D D Stereospecific catalyst (SS) — — — L L L L L Catalystratio (NSS/SS) — — — 91/1 91/1 91/1 91/1 91/1 Target a-PP/i-PP ratio 1/01/0 1/0 8/1 8/1 8/1 8/1 8/1 Diolefin used (ml) 0.2 0.4 1 .0 0 0.2 0.41.0 2.0 Diolefin (ppm) 1,852 3,704 9,259 0 1,852 3,704 9,259 18,519Yield (g) 38.1 32.5 25.2 64.8 34.1 31.6 32.4 30.2 Polymerization Temp.(° C.) 60 60 60 60 60 60 60 60 Density (g/cm³) 0.8690 0.8705 0.87500.868 0.8750 0.8760 0.8765 0.8795 T_(m) (° C.), 2nd melt — — — 144 144140 139 134 Heat of fusion (J/g) 0 0 0 12 8 9 13 13 Degree ofcrystallinity (%) 0 0 0 6 4 5 7 7 M_(n) (× 1,000) 238 252 — 136 183 179— — M_(w) (× 1,000) 450 537 — 271 361 403 — — M_(z) (× 1,000) 761 1,014— 455 586 711 — — M_(w)/M_(n) 1.89 2.13 — 1.99 1.97 2.25 — — M_(z)/M_(n)3.19 4.03 — 3.35 3.20 3.97 — — g_(w) — — — 1.05 1.05 0.98 — — g_(z) — —— 1.05 1 .04 0.95 — — Initial modulus (PSI) 276 288 291 621 693 9461,175 1,383 Yield stress (PSI) — — — 143 — — — — Yield strain (%) — — —76 — — — — Stress at 100% strain 123 126 127 149 175 199 337 304 Stressat 500% strain 177 201 253 132 198 246 712 705 Tensile strength (PSI)189 225 738 154 224 443 956 856 Strain at break (%) >3,500 >3,500346 >3,400 >3,400 2,304 649 635 Recovery from 100% strain 87 88 86 81 9288 87 86 Recovery from 500% strain 82 88 86 69 82 83 84 84 Recovery from1,000% strain 77 84 — 77 78

TABLE 3 Comparison of Mechanical Properties, Composition of theInvention vs. Blends Example 19 20 21 22 23 24 25 26 27 28 29Comparative/Invention C I I I I I C I I I I Non-stereospecific catalyst(NSS) D D D D D D D D D D D Stereospecific catalyst (SS) L L L L L L Q QQ Q Q Catalyst ratio (NSS/SS) 11/1 11/1 11/1 11/1 11/1 11/1 100/1 100/1100/1 100/1 100/1 Target a-PP/i-PP ratio 1/1 1/1 1/1 1/1 1/1 1/1 88/1288/12 88/12 88/12 88/12 Diolefin used (ml) 0.0 0.1 0.2 0.4 1.0 2.0 0.00.2 0.4 1.0 2.0 Diolefin (ppm) 0 926 1,852 3,704 9,259 18,518 0 1,8523,704 9,259 18,518 Yield (g) 35.9 37.0 39.6 34.4 29.5 39.5 36.4 40.23713 40.5 35.4 Polymerization Temp. (° C.) 60 60 60 60 60 60 60 60 60 6060 Density (g/cm³) 0.8770 0.8750 0.8820 0.8840 0.8880 0.8875 0.87950.8790 0.8800 0.8850 0.8875 T_(m) (° C.) 141 140 144 140 141 1 36 157152 148 144 137 Heat of fusion (J/g) 36 41 53 49 60 51 24 13 24 25 21Degree of crystallinity (%) 19 21 28 26 32 27 13 7 13 13 11 M_(n) (×1,000) 124 115 95 109 128 123 — — — — — M_(w) (× 1,000) 261 247 209 251310 421 — — — — — M_(z) (× 1,000) 467 466 437 514 737 1,317 — — — — —M_(w)/M_(n) 2.10 2.15 2.20 2.30 2.42 3.42 — — — — — M_(z)/M_(n) 3.774.05 4.60 4.72 5.76 40.71 — — — — -1 Initial modulus (PSI) 13,600 13,53016,770 20,160 19,820 19,770 1,445 2,416 1,990 4,050 2,378 Yield stress(PSI) 710 701 994 1,089 1,118 1,255 — — — — — Yield strain (%) 21 21 2618 18 25 — — — — — Stress at 100% strain 705 660 930 1,000 1,049 1,186280 371 384 827 851 Stress at 500% strain 972 987 1,311 1,424 1,6961,928 460 557 649 1,993 Tensile strength (PSI) 1,306 1,174 1,972 1,8392,364 2,734 609 892 930 1,771 1,239 Strain at break (%) 770 660 866 718726 761 1,068 1,096 908 403 228 Recovery from:100% strain 60 50 60 50 4656 87 89 83 82 84 Recovery from:500% strain 30 22 31 26 21 27 74 85 75 ——

Examples 2-5 as compared to comparative Example 1 show that crosslinkinghas occurred via incorporation of the di-vinyl monomer as evidenced bythe continued decrease in g_(w) and g_(z), as the amount of the di-vinylmonomer is increased. This is further supported by Examples 7-10 ascompared to comparative Example 6 and Examples 15 and 16 as compared tocomparative Example 14. These examples show that a partially crosslinkedmixture of isotactic and atactic polypropylene has been produced by thenovel process of this invention. A decrease in the g_(w) and g_(z), isknown to indicate the presence of branched polymer chains which canresult primarily from multipe occurrences of the connection of polymersegments via incorporation of a single di-vinyl monomer into twoseparate polymer segments.

Comparative Examples 11-13 show crosslinked atactic polypropylenecompositions. These examples show that crosslinking alone without theuse of the strereospecific catalyst produces compositions havinggenerally poorer initial modulus, tensile strength, and recovery thanthose of Examples 15-18, which use similar process variables but use astereospecific catalyst in addition to the non-stereospecific catalyst.

Examples 20-24 show the trend toward increased tensile strength andinitial modulus as diolefin addition is increased while maintainingapproximately the same recovery from 100% strain relative to comparativeExample 19 without diolefin.

Examples 26-29, using a different stereospecific catalyst, again showthe trend toward increased tensile strength and initial modulus asdiolefin addition is increased while maintaining approximately the samerecovery from 100% strain relative to comparative Example 25 withoutdiolefin.

Although the invention has been described with reference to particularmeans, materials and embodiments it is to be understood that theinvention is not limited to the particulars disclosed and extends to allequivalents within the scope of the claims.

What is claimed is:
 1. A process for preparing a polymer compositioncomprising combining under polymerization conditions at least oneα-olefin monomer containing 3 or more carbon atoms and at least onediolefin monomer in the presence of: a) at least one non-stereospecificmetallocene catalyst system selected for its capability forincorporating said diolefin monomer into an amorphous copolymer of saidα-olefin and said diolefin monomer; and b) at least one stereo-specificmetallocene catalyst system selected for its capability forincorporating said diolefin monomer into a crystalline copolymer of saidα-olefin and said diolefin monomer.
 2. The process of claim 1 whereinsaid alpha olefin contains from 3 to 30 carbon atoms.
 3. The process ofclaim 2 wherein said alpha olefin is propylene, butene-1, or acombination thereof.
 4. The process of claim 1 wherein said alpha olefincontains from 3 to 20 carbon atoms.
 5. The process of claim 1 whereinsaid diolefin monomer contains two olefinic unsaturations which are ofsubstantially equal reactivity under metallocene polymerizationconditions.
 6. The process of claim 1 wherein said diolefin monomer is adi-vinyl monomer.
 7. The process of claim 1 wherein thenon-stereo-specific metallocene catalyst system is selected from[dimethylsilanediyl(tetramethylcyclopentadienyl)(cyclododecylamido)]metaldichloride;[dimethylsilanediyl(tetramethylcyclopentadienyl)(t-butylamido)]metaldichloride; and[dimethylsilanediyl(tetramethylcyclopentadienyl)(exo-2-norbornyl)]metaldichloride; wherein the metal is, at least one of Zr, Hf, or Ti.
 8. Theprocess of claim 1 wherein the stereo-specific metallocene catalystsystem is selected from the racemic isomers of:[dimethylsilanediylbis(2-methyl-4-phenylindenyl)]metal dichloride;[dimethylsilanediylbis(2-methyl)]metal dichloride;[dimethylsilanediylbis(indenyl)metal dichloride;[dimethylsilanediylbis(indenyl)metal dimethyl;[dimethylsilanediylbis(tetrahydroindenyl)metal dichloride;[dimethylsilanediylbis(tetrahydroindenyl)metal dimethyl;[dimethylsilanediylbis(indenyl)metal diethyl; and[dibenzylsilanediylbis(indenyl)metal dimethyl; wherein the metal is atleast one of Zr, Hf, or Ti.
 9. The process of claim 1 wherein saidpolymerization is carried out in one reaction vessel.
 10. The process ofclaim 1 wherein the ratio of said non-stereospecific catalyst to saidstereospecific catalyst is in the range of from 20:1 to 120:1.
 11. Theprocess of claim 1 wherein the polymerization is carried out at atemperature in the range of from −100° C. to 300° C.
 12. The process ofclaim 1 wherein the polymerization is carried out at a pressure in therange of from 0.019 psia to 50,000 psia.
 13. The process of claim 7wherein the metal is Ti.
 14. The process of claim 8 wherein the metal isZr.